1. Field of the Invention
The present invention relates to a method for adhering a film on the surface of a cathode ray-tube (CRT), more specifically, relates to a method of adhering a functional film on the surface of a cathode ray-tube in by which the film can be adhered well to the surface of the panel glass of the cathode ray-tube.
2. Description of the Related Art
The panel glass of a cathode ray-tube is produced by shaping melted glass by a mold, but unevenness is caused on the surface of the panel glass at the time of shaping, and therefore the surface of the panel glass is polished before use. In the process of production of panel glass, the time and cost taken for polishing the surface of the panel glass and polishing the sealing edge of the panel account for 20 to 30 percent of the cost of the panel. To answer the demand for reduction of the production costs of cathode ray-tubes, it is necessary to streamline the polishing steps.
Also, the increasingly large size of cathode ray-tubes and the flattening of the panel have led to a tendency to make the panel glass thicker so as to achieve the predetermined explosion-prevention performance, but when the panel glass becomes thick, the weight is increased, which is not preferred.
In view of these circumstances, a method in which the thickness per se of the panel glass is kept thin, and the functional glass is bonded to the surface of the panel glass via an adhesive (PPG laminate system) or a method of bonding a transparent functional film to the surface of the panel glass via an adhesive have been proposed.
In the former PPG laminate system, although the finish polishing of the panel glass is eliminated, there are complicated steps of taping etc. The latter method is considered more promising.
Further, in the latter system, there is the effect of protecting the surface of the panel of the cathode ray-tube and prevention of low reflection and static electricity.
In the related art, one of the methods of adhering film in such a cathode-ray tube was to use an adhesion roller.
As shown in FIG. 1A, in this method, first a film 1 to be adhered is sandwiched between a roller 3 of an adhesion roller 2 and a feed roller 4. As shown in FIG. 1B, the adhesion roller 2 is moved downward and the film 1 is pushed against one end portion of the surface of the panel 5. In this case, as the adhesive, for example an ultraviolet ray-curable resin is coated on the entire surface of the panel 5. Then, as shown in FIG. 1C, by rolling the roller 3 in this state and moving the adhesion roller 2 to the other end portion of the surface of the panel 5, the film 1 is brought into tight contact with the surface of the panel 5.
Thereafter, by irradiating the entire surface from the top of the film 1 with ultraviolet rays, the resin between the surface of the panel 5 and the film 1 is cured and therefore the film 1 is bonded to the surface of the panel 5.
However, in this conventional method, the following problem has occurred.
Namely, as shown in FIG. 1B, when the roller 3 is rolled from one end of the surface of the panel 5, normally air bubbles inside the adhesive resin produced near its starting end are pushed out to the terminal end of the surface of the panel 5, but these air bubbles sometimes remain in the resin in the middle of the adhesion process. Such air bubbles become a cause of "glitter" on the effective screen. For this reason, in the past, a method of adhering film with which air bubbles do not remain in the resin of the adhesive has been demanded.
Also, in the method of bonding a functional film to the surface of panel glass via an adhesive, an ultraviolet ray-curable resin is used as the adhesive, however, so there are the following problems.
Namely, there are the problems that the UV resin is cured by the ultraviolet rays, but since the UV resin protruding from the functional film comes into contact with the air, it is difficult to cure, is sticky on the surface, and is apt to catch dirt or dust.
Therefore, development of a UV resin which is sufficiently cured even in the air once irradiated by ultraviolet rays has been demanded, but no UV resin of a low cost having such properties has yet been developed. Also, although increase of the energy output of the UV irradiation, treatment in an oxygen-depleted state, etc. were investigated, the fact is that no definitive means for solving the problem had yet been found.
Moreover, investigation was also made of coating a modified acrylate-based adhesive such as Hardlock (trademark of Denki Kagaku Co.) on the part of the UV resin protruding from the functional film, it cannot be used due to the problem of a yellow discoloration of the resin film, bubbles, etc.
Therefore, in the past, the practice has been to adhere polyester tape or the like on the UV resin protruding from the functional film, but this has the problem that the work is troublesome.